Process of making cellulosic esters containing halogen-substituted fatty-acid groups



Patented Jan. 8, 1929.

HANS T. CLARKE AND CARL J. MALM, or ROCHESTER, NEW Y RK, ASSIGNORS T0 EAST- MAN KODAK COMPANY, or ROCHESTER, new YORK, A coRroRA'rIoN OF NEW YORK.

PROCESS OF MAKING CELLULOSIG ESTEBS CONTAINING HALOGEN-SUBSTITUTED FATTY-ACID GROUPS.

No Drawing.

This invention relates to processes of making cellulosic esters containing halogen-substituted fatty acid groups. One object of the invention is to provide a simplified and relatively inexpensive process for making such esters by a single reaction. Other objects will hereinafter appear.

We have found that such esters may be made by subjecting cellulosic material to the coaction of a halogen-substituted fatty acid containing more than five carbon atoms and an organic acid anhydrid which impels this esterification but does not itself contribute any cellulose esterifying groups to the product. Moreover, the anhydrid is converted into an acid which does not contribute any groups to the ester.

The presence of substituted halogens in fatty acids either retards or prevents the formation of cellulose esters of such acids under conditions which will formuseful or substantially undegraded esters. When the fatty acid contains five, carbon atoms or less, the inhibiting effect of the halogen, whether the latter be in the alpha or other-position,

prevents esterification for all practical purposes But when the halogen-substituted fatty acids contain more than five carbon atoms, useful cellulose esters containing them can be prepared by our process by a single reaction. is thus the determining factor and not the alpha or other position of the halogen atoms. The greater the number of carbon atoms, provided there are more than five, the morev readily can the esterification be brought about in spite of the opposing effect of the halogen atoms. stearic acid is readily esterified with cellulose by our process, while halogen-substituted caproic acid is esterified more slowly. The intermediate members of the halogen-substituted fatty acid series, such as halogen-substituted heptylic, caprylic, pelargonic, capric, lauric, myristic, palmitic and margaric acids can be esterified with cellulose with intermediate ease of reaction. Of the halogen-substitutedhigher fatty acids which we can employ, we prefer to selectthe mono, di, tri or tetra brom or chlor members of the series. The correspondmg 1od1n'e compounds are expenslve.

The length of the carbon chain For example, halogen-substituted Application filed January 18, 1928. Serial No. 247,742.

,mixtures of them. The reaction can be-carried out using mono, di andtrichlor and brom propionic and butyric anhydrids. But they are relatively too expensive, without any compensating advantage. Likewise/the corresponding iodine-substituted acetic, propionic and butyric anhydrids cost too much. But anhydrids other than halogen-substituted .ones can also be employed, such as methoxy' acetic anhydrid and its higher alkyl homologues beginning with ethoxy acetic anhydrid. It is a characteristic of all of the above named anhydrids that they do not contribute groups to the ester. For example, the celluloseesters produced contain no chloracetic groups when chloracetic anhydrid is employed, nor any methoxy acetic groups when methoxy acetic anhydrid is used.

As the cellulosic materials to be esterified, we can use any customarily employed in the manufacture of the hitherto known cellulosic esters, For instance, cotton fiber tissue paper, clean cotton, surgical cotton wool, and even bleached sulfite wood pulp are useful .These materials, especially the cotton ones,

are sufficiently undegraded when they enter the reaction, so that they yield esters of good. flexibility. Of course, our ,process can be applied to the esterification of chemically affected cellulosic materials, such as so-called hydrocellulose, reverted cellulose from the viscose or cuprammonium processes, lower cellulose nitrates, lower ethyl celluloses, etc.

The temperature at which our process .is conducted must obviously be above the melting point of the ingredients of the esterifying" bath, but it should not rise to a point where, the products are degraded, as indicated by the poor quality of ,films prepared from the resulting esters. The melting points of the esterifying baths are lower than the melting strong splvent action upon the acids which are employed, thus tending to insure good working baths. It is convenient, although not essential, to have an additional solvent present which will not enter into the reaction. We have found monochloraoetic acid to be useful for this purpose. And as the reaction proceeds, further amounts of monochlorace'tic acid are formed and likewise add to the fluidity of the bath Under these circumstances, temperatures between 50 C. and 80 C. are satisfactory, to C. being preferred.

The reaction can be hastened and more thorough results obtained when a catalyst is present- We may use any of the customary esterifying catalysts, but we prefer the milder ones, such as the perchlorates disclosed in United States Patent No. 1,645,915, Carl J. Malm, October 18, 1927, process of making cellulose esters of organic acids. Zinc chlorid is likewise usable, as well as the red phosphorus and chlorine of United States Patent N 0. 1,591,590, William R. lVebb and Carl J. Malm, July 6, 1926. y I

We shall now describe several examples of our invention, but it will be understood that the latter is not limited to the illustrative details thus set forth, except as indicated in the appended claims. A reaction bath is prepared by warming at 60 to 65 C. for 1 to 2 'hours the following mixture,8 parts by weight. of cellulose, 40 parts by weight of chloracetic anhydrid, 20 parts by weight of chloracetic acid and .05 parts by weight of magnesium perchlorate trihydrate. For conveniencewe shall hereinafter refer to this as the standard bath. Into this bath there are thoroughly stirred 15part's by weight of alpha bromo stearic acid and 4 parts by weight .of acetic acid. By maintaining a temperature between 60 and 65 0., a clear dope forms in about 6 hours, indicating the completion of the reaction. The product is isolated by pouring intomethyl alcohol and washing the precipitate with this same liquid. The cellulose-aceto-alpha-bromo-stearate thus produced contains 11.3% of bromine I and is soluble in acetone, chloroform, benzene,

or mixtures of these, and can be deposited from its solutions in the form of transparentflexible films which are substantially noninflamma'ble,that is, will not burn with a sustained flame when held in the presence of an igniting flame.

In another example of our invention there are stirred into the standard bath hereinabove described 17 parts by weight of 9-l0-dibromo stearic acid and 7 parts by weight of acid).- 'After about 6 hours at 60 to 65 C.

acetic acid (this halogen-substituted stearic acid is readily prepared by brominating oleic the reaction is complete, as indicated by the formation ofv a clear homogeneous dope, which is precipitated in methyl alcohol and the product washed with the-same substance.

The product contains 23% of bromine, is

soluble in acetone, in chloroform and in benzone, or mixtures of these liqulds, andde- 'of dichloro stearic' acid (obtained by chlorinating oleic acid) and 5 parts by weight of acetic acid. After 6 hours at 60 to 65 C. the clear dope is poured into methyl alcohol with vigorous stirring and the precipitate washed until purified. It contains 8.5% of chlorine and is soluble in acetone and in chloroform, or mixtures of them; but isinsoluble in benzene. It yields flexible, transparent films.

In yet a different example of our invention there are added to the standard bath hereinabove described 14 parts by weight of tetrachloro steario acid'and 5 parts by weight of acetic acid (the first-named acid may be prepared by adding chlorine to the acid formed upon sap'onification of linseed oil). After 6 hours at 60 to 65 C. the solution becomes clear enough and is poured with agitation into methyl alcohol and the precipitate washed with said alcohol. The cellulose aceto-tetrachloro stearate 'thus produced contains 14% of chlorine and is soluble in acetone and chloroform or mixtures of them, but not in benzene. It forms flexible, transparent films'of very low inflammability.

In another example of our invention 10 parts by weight of alpha bromo caproic acid and 4 parts by weight of acetic acid are stirred intothe standard bath hereinabove described." This is heated at 60 to 65 C.

produced by our process yield flexible films or filaments without softeners or plastifiers, but chloroform-soluble or acetone-soluble plastifiers or softeners heretofore used with cellulose acetates may be employed with them, triphenyl and tricresyl phosphates being examples of the large number that can be employed. Our compounds can be mixed or laminated with cellulose nitrate or acetate by means of acommon solvent. Films of them can be backed with a cellulose acetate layer or with hygroscopic nitrocellulose coatings to prevent static, or nitrocellulose or acetate films may be backed with thin layers of our compounds. In short, our process can produce products of technical importance in thepreparation of films for photographic purposes, filaments for rayon, lacquers, artificial leather, moldable plastics, etc.

Having thus described ourinvention, What we claim as new and desire to secure by Letters Patent is:

1. In the process of making cellulosic esters containing halogen-substituted fatty acid groups, subjecting cellulosic material to the ooaction of a halogen substituted fatty acid containing more than five carbon atoms and an organic acid anhydrid which impels such .esterification but is free from celluloseesterifying groups and during the esterification is converted into a compound that is also free from cellulose-esterifying groups.

2. In the processof making cellulosic esters containing halogen-substituted fatty acid grou s, treating cellulosic material with an esteri ying bath containing a halogensubstituted fatty acid having more than live carbon atoms and a halogen-substituted fatty acid anhydrid having less than ten carbon atoms.

3. In the process of making cellulose esters containing halogen-substituted fatty acid groups, treating cellulosic material with an esterifying bath containing a halogen-substituted fatty acid having'more than five carbon atoms, and chloracetic anhydrid.

4. In the process of making cellulosic esters containing a halogen-substituted stearic acid group, subjecting cellulosic material to the coaction'of a corresponding halogen-substituted stearic acid and a halogensubstituted fatty acid anhydrid having "less than ten carbon atoms.

5. In the process of making a cellulose est-er containing a brom-substituted stearic acid group, treating cellulosic material in a bath.

containing brom-substituted stearic acid and chloracetic anhydrid. Signed at Rochester, New York,-this 10th day of January, 1928.

HANS T. CLARKE. CARL. J. MALM. 

